The invention relates to a pole for a magnet which can be used in particular in a hydraulic solenoid valve. The invention also relates to a magnet and to a hydraulic solenoid valve.
The poles known from the prior art have the disadvantage of a high degree of inertia. For this reason, in particular hydraulic solenoid valves are complicated to activate. Furthermore, the poles known in the prior art have a high degree of friction. Furthermore, when mounting it is necessary to take care that there are no air bubbles in the interior of the armature space because the poles known from the prior art have a modified dynamic depending on the proportion of air in the armature space.
Furthermore, the poles known from the prior art have the disadvantage of marked wear.
The object of the invention is therefore to provide a pole which has a low degree of wear and is highly responsive. The pole which is to be provided is to be insensitive to proportions of air in the armature space and to be of simple design. It is also the object of the invention to provide a magnet which is improved in this respect and a hydraulic solenoid valve which is improved in this respect.
This object is achieved by means of the subject matter of the independent claims. Advantageous refinements emerge from the respective subclaims.
With such a configuration, the magnet armature moves transversely with respect to the longitudinal axis when current flows through the electrical coil. Because of the particular interrupted construction of the coil core in the region of the magnet armature, the magnetic field lines emerge, in fact, from a first coil core section, into the magnet armature and out again and then into a second coil core section. Owing to the armature side faces which are of xe2x80x9cobliquexe2x80x9d construction with respect to the longitudinal axis, a force component which extends transversely with respect to the longitudinal axis and acts on the magnet armature is produced, said force component displacing the magnet armature, and thus the armature tappet connected to the magnet armature, transversely with respect to the longitudinal axis. According to the invention, this transverse movement is used to activate, in particular, a valve slide of a hydraulic solenoid valve.
According to the invention, the magnet armature can also have two armature side faces which are cut from the longitudinal axis with an angle other than 90xc2x0, the two armature side faces being constructed in a preferred embodiment so as to be symmetrical with respect to a plane extending perpendicular to the longitudinal axis. In particular with this construction of the two armature side faces, the components of the force acting on the magnet armature which are generated as a result of the magnetic flux and extend in the direction of the longitudinal axis cancel each other out so that there is no additional loading in the longitudinal direction of the armature tappet. This increases the operational reliability of the pole according to the invention. In addition, a transverse force component whose absolute value is doubled in comparison with a single, obliquely arranged armature side face acts on the magnet armature. This improves the efficiency of the pole according to the invention.
According to the invention, the coil core can have at least one or even two core side faces which are cut from the longitudinal axis at an angle other than 90xc2x0, it being possible for the two core side faces to be constructed so as to be symmetrical with respect to a plane running perpendicular to the longitudinal axis. Constructing the coil core in such a way improves the guidance of the magnetic field lines in the interior of the pole according to the invention, which increases its efficiency. It is particularly advantageous here if in each case one armature side face extends essentially parallel to a core side face lying opposite it because the course of the magnetic field lines in the pole according to the invention can then be configured particularly satisfactorily. Furthermore, the behavior of a pole which is configured in this way can be modeled and predicted particularly satisfactorily so that in particular also linear activation processes and precise adjustments are made possible.
In the configurations of the pole according to the invention described above, the designation xe2x80x9cessentially parallelxe2x80x9d with respect to the position of armature side faces and core side faces means that in each case one core side face extends parallel to an armature side face in at least one activation state of the magnet armature. It is not excluded here that when the magnet armature is displaced one armature side face assumes in each case a position with respect to a core side face in which they no longer extend parallel to one another. Such states can arise in particular when there are large displacements of an armature tappet which is mounted on only one side.
Furthermore, it is possible to provide in the interrupted region of the coil core a connecting region made of antimagnetic material which connects sections of the coil core to one another. This results in a compact and stable design of the coil core which is also sealed to prevent hydraulic fluid escaping.
In the interrupted region of the coil core, it is also possible to provide a connecting region which has magnetizable material. As a result, an additional air gap can be provided which, before the actual switching of the magnet by an electrical coil in the region of the magnet armature, can be brought to saturation by an electrical coil in the region of the magnet armature. This results in the armature being additionally acted on in its direction of movement even before the magnet armature according to the invention actually switches. In such a state, the magnet armature according to the invention is kept in a starting position from which it can be moved into its switched position by increasing the current. Here, the force generated by the additional air gap does not increase further because said air gap is preferably saturated. However, the force generated by a working air gap between the pole and the magnet armature increases with the increase in the magnetic field density in the region of the pole. As soon as the force in the working air gap is greater than the force in the additional air gap, the magnet armature moves in the direction of the force generated in the working air gap. The force which is generated in the additional air gap decreases with a very steep characteristic curve because the associated air gap becomes larger and because at the same time the working air gap becomes smaller. As a result, the force generated in the working air gap is available immediately, and to its full extent, for switching a magnet provided with the pole according to the invention. Furthermore, there are hardly any decelerations due to eddy currents if the main part of the magnetic field in the working air gap has already been built up by a biasing current.
The development according to the invention provides numerous advantages. For example, the current has to be increased only to a small extent to switch the magnet according to the invention. At the same time, hardly any eddy current decelerations occur during the switching, and a high switching force is available just after the start of the stroke of the magnet armature. The armature according to the invention can be used particularly advantageously in conjunction with the particular advantages of a swivel armature magnet which is obtained in such a way, namely those of a low armature mass and of negligible friction of the armature within the pole, and by preventing an increase in mass as a result of oil which is to be expelled through narrow drilled holes.
The pole according to the invention can be manufactured easily if the coil core and/or the magnet armature are each constructed as an essentially cylindrical tubular section. Here, the magnet armature is preferably constructed in such a way that it can be permanently attached to a bar-shaped armature tappet while the coil core has a through-opening which is constructed in such a way that the armature tappet does not bear against the inside of the coil core even when there are large displacements of the magnet armature.
If a first end of the armature tappet is permanently connected to a first end of the coil core, when a displacement occurs the magnet armature moves on an orbit about the mounting point of the armature tappet on the coil core. A transverse movement of the magnet armature which occurs here can then be transmitted particularly easily to, for example, a valve slide of a hydraulic solenoid valve. There is also provision here that a second end of the armature tappet projects beyond a second end of the coil core. In order to activate, for example, a valve slide, it is then sufficient to mount the coil core in a valve housing and to bring the second end of the armature tappet into contact with the valve slide.
The invention is also implemented in a magnet, in particular for a hydraulic solenoid valve, which has a pole which is configured according to the invention as described above, at least one electrical coil also being provided in the region of the coil core.
The invention is also implemented in a magnet which has two electrical coils which are preferably arranged coaxially with respect to one another. It is particularly advantageous here if use is made of a magnet pole in which a connecting region with magnetizable material is provided in the interrupted region of the coil core. With two such coils it is particularly easily possible to achieve premagnetization, which permits improved operation with a second air gap.
In contrast to the above, or in addition thereto, it may be possible to apply not only two different operating voltages but also three different operating voltages to the electrical coil or coils. Here, it is possible to switch, starting from a quiescent potential which constitutes the first operating voltage, via the second operating voltage into the third operating voltage. The second operating voltage generates here the premagnetization, while the third operating voltage constitutes the actual switching current of the magnet.
According to the invention, the magnet armature can, however, also be premagnetized by means of a permanent magnet.
In addition, the invention also relates to a hydraulic solenoid valve with at least one magnet according to the invention, the solenoid valve having a valve slide which can be activated by the armature tappet.
The swivel arm magnet according to the invention as described above is particularly advantageous because it operates with low friction and as a result has no wear, or only a small degree of wear. Furthermore, it is highly responsive because it is not necessary to overcome any static friction in order to activate it. In particular in the construction with two obliquely extending working gaps which are symmetrical with respect to one another, the particular advantage is obtained that no resulting force occurs in the axial direction of the armature tappet which is to be bent. In addition, the magnet armature can be made particularly small, which improves the actuation characteristics of the magnet according to the invention. Furthermore, the magnet according to the invention does not have any reduced oil mass so that no significant dynamic differences occur irrespective of whether there is oil or air in the armature space. Finally, the magnet according to the invention is of particularly simple design.
The invention is also embodied in the form of a pole which has a magnet armature in which the armature side faces intersect the longitudinal axis at a right angle if at the same time the coil core has, in the region of the magnet armature, at least one core side face which is intersected by the longitudinal axis at an angle other than 90xc2x0. Even with such a construction which is reversed in comparison with the configurations described above, the field lines in the air gap extend between the magnet armature and coil core in such a way that a force component which extends perpendicularly to the longitudinal axis and deflects the magnet armature is produced.